Hcg levels

Erin • Married ❤️ Mommy to Ava Noelle 11/17/17 💜
So I went on Monday for bloodwork and my levels came back at 510 for hcg and my progesterone was 76. I had to go back again today to see if they doubled and it only went up to 654 😞 I've already had 2 miscarriages so I'm being cautiously optimistic but has this happened to anyone else early on in pregnancy? I'm about 4 weeks 3 days and have to go back tomorrow or Saturday for repeat bloodwork.